1. Field of the Invention
The present invention relates to a thin-film magnetic head for applying to magnetic recording, especially relates to a tape head for writing data to a magnetic tape and reading data from the tape. The present invention further relates to a magnetic tape apparatus having the tape head. Furthermore, the present invention relates to a controlling method of magnetic spacing, which is a distance between the ends of head elements in the thin-film magnetic head and the surface of the magnetic recording layer of a magnetic recording medium.
2. Description of the Related Art
In recent years, magnetic recording and reproducing apparatuses have been remarkably improved in capacity of storage data, corresponding to the widespread use of multimedia and the Internet. And magnetic tape apparatuses, for example, for backing up or storing data or for recording and reproducing audio video information are no exception of this trend of larger capacity, and have been required to be improved in areal recording density corresponding to the larger capacity.
Thin-film magnetic heads are widely used, in the above-described magnetic recording and reproducing apparatuses, for writing data to a magnetic recording medium and reading data from the medium. The thin-film magnetic heads have also been strongly required to be improved in performance corresponding to the larger capacity. Especially, significantly required is to appropriately control a magnetic spacing in order to stably perform read and write operations under higher recording density and to maintain original lifetime of the thin-film magnetic head. Here, the magnetic spacing is defined as a distance between the ends of head elements in the thin-film magnetic head and the surface of the magnetic recording layer of a magnetic recording medium.
As a measure for positively controlling the magnetic spacing, Japanese Patent Publication No. 2006-031817A describes a technique in which the head end surface is protruded toward the magnetic disk by the heat generated from a heater provided within the thin-film magnetic head for magnetic disk apparatuses. Further, Japanese Patent Publication No. 09-198829A describes a technique for dissolving the adsorption between the head and the magnetic disk by using a heater.
Also in the thin-film magnetic head for magnetic tape apparatuses (tape head), it is significantly important to adjust the degree of contact between the tape head and the magnetic tape, and thus to appropriately control the magnetic spacing. As an example of intending to control the magnetic spacing, Japanese Patent Publication No. 2004-295951A describes a technique of utilizing a negative-pressure slider for hard disks. Further, U.S. Pat. No. 6,122,147 (Japanese Patent Publication No. 2000-207800A) discloses a technique in which cavities are provided in a tape bearing surface (TBS), which is a medium-opposed surface or a sliding surface, and the cavities deform portions of the magnetic tape that passes above the cavities, to stabilize the contact between the magnetic head and the magnetic tape.
However, there has been a problem that the magnetic spacing is likely to vary due to the change in shape of the medium-opposed surface of the thin-film magnetic head, the change generated by the contact between the head and the medium. Especially, the tape head slides on the magnetic tape during read and write operations. Therefore, the shape of the tape bearing surface (TBS), which is a medium-opposed surface as well as a sliding surface, varies over time due to the friction with the magnetic tape. The variation of the shape becomes larger in the case that the magnetic tape contains abrasive. In addition, the just-described problem may become more serious due to the error in adhering position of a closure occurred when the closure is adhered during manufacturing process of the tape head.
In the process of manufacturing the head, the error in adhering position which occurs when the closure is adhered on an overcoat layer is generally on the order of several hundred nm (nanometers). After the adhesion, lapped are the surfaces on the side opposed to the medium of the closure and overcoat layer. Even so, the thus-formed medium-opposed surfaces of the closure and overcoat layer have positions different from each other. That is, a step of the order of at least several nanometers (nm) is generated in the boundary between the closure and the overcoat layer. Here, in the case that, as the result of adhering and lapping, the height of the medium-opposed surface of the closure becomes larger than the desired one, that is, in the case that the medium-opposed surface of the closure is more protruded toward the magnetic tape, the magnetic spacing may become larger, which would be likely to cause the read output to be decreased, or to cause the peak steepness of the read signal to be degraded. Whereas, in the case that the height of the medium-opposed surface of the closure becomes smaller than the desired one, the lifetime of the tape head would be likely to be reduced because the magnetic spacing excessively decreases due to the wear of the head elements generated from the increase in the degree of contact between the head elements and the magnetic tape. Further, the head performance may be degraded due to frictional heat generated by the contact.
Here, the height of the medium-opposed surface of the closure is defined as a distance from the medium-opposed surface of the overcoat layer to the medium-opposed surface of the closure in the direction perpendicular to the medium-opposed surface of the closure (height direction). The height is exemplified by HC0 in FIG. 4a attached to the present specification.